Add a unit test for the expected behaviour when inheriting from an un…

…parameterized generic base class (#40)

* Add a unit test for the expected behaviour when inheriting from an unparaemterized generic base class

* update changelog

* update test

* fix mypy

.changelog/_unreleased.toml

@@ -3,3 +3,11 @@ id = "0285c33d-85e6-4d72-bf09-7f8812b75e36"
 type = "fix"
 description = "Fix star import from `typeapi`"
 author = "@NiklasRosenstein"
+pr = "https://github.com/NiklasRosenstein/python-typeapi/pull/39"
+
+[[entries]]
+id = "233e97d3-9e6c-4330-ac8d-fe4a9ad8e3a5"
+type = "tests"
+description = "Add a unit test for the expected behaviour when inheriting from an unparameterized generic base class"
+author = "@NiklasRosenstein"
+pr = "https://github.com/NiklasRosenstein/python-typeapi/pull/40"

src/typeapi/typehint_test.py

@@ -274,6 +274,47 @@ def test__TypeHint__from_newtype() -> None:
  assert hint.hint is MyInt
 
 
+def test__TypeHint__from_generic_with_unbound_typevar() -> None:
+ """
+ Inheriting from a generic base class without parameterizing it is not valid and databind cannot handle the
+ case correctly. The `TypeHint.bases` will appear as the bases' bases (that is because `__orig_bases__` is not
+ set on the new subclass and instead it reads the attribute from the parent).
+ """
+
+ T = TypeVar("T")
+ U = TypeVar("U")
+
+ class Base(Generic[T]):
+ a: int
+
+ class Incorrect(Base): # type: ignore[type-arg]
+ b: str
+
+ class Correct(Base[U]):
+ b: str
+
+ hint = TypeHint(Base)
+ assert isinstance(hint, ClassTypeHint)
+ assert hint.type == Base
+ assert hint.bases == (Generic[T],)
+ assert hint.origin is None
+ assert "__orig_bases__" in vars(Base)
+
+ hint = TypeHint(Incorrect)
+ assert isinstance(hint, ClassTypeHint)
+ assert hint.type == Incorrect
+ assert hint.bases == (Generic[T],) # Note how this is not (Base,)
+ assert hint.origin is None
+ assert "__orig_bases__" not in vars(Incorrect)
+
+ hint = TypeHint(Correct)
+ assert isinstance(hint, ClassTypeHint)
+ assert hint.type == Correct
+ assert hint.bases == (Base[U],) # type: ignore[valid-type]
+ assert hint.origin is None
+ assert "__orig_bases__" in vars(Correct)
+
+
 def test__ClassTypeHint__parametrize() -> None:
  """This method tests the infusion of type parameters into other types.